Calendar from OSS to NE on new server

We've been running Zimbra OSS (on Debian) for a while now and would like to move to the NE (looks like Ubuntu is our best option for this). I think we should be OK to get all of the mail across (using imapsync) and the contacts (using csv export/import, but how do we get the calendars over?

So, how do we get our calendars from the current server to our new one?

Also, when I set up the original server I gave it the name zimbra.ourdomain.com, but this means that all the accounts seem to appear as someone@zimbra.ourdomain.com instead of just someone@ourdomain.com. We have set the reply addresses so that things work properly, but I was wondering if there is a way of doing this differently when we install the NE box?